[Elecraft] Bird 43 Wattmeter calibration

[G3VVT at aol.com]

As well as the individual calibration on the slugs there is another  
calibration pot inside the Bird 43 feeding the meter movement if my memory is  correct.
 
You need to compare the meter and slugs against a known standard or a  
recently calibrated power meter into an accurate dummy load. Installing a  known 
good slug would allow you to check out the meter body. If it is within 10%  leave 
it as is.
 
"If it ain't broke don't fix it"
 
Bob, G3VVT